This invention relates to a process for producing hydrocarbons useful as diesel fuel and aviation fuel from renewable feedstocks such as the glycerides and free fatty acids found in materials such as plant and animal oils. The process involves hydrogenation, deoxygenation, hydroisomerization, and selective hydrocracking in one or more reactors to generate both a diesel fuel product and an aviation fuel product.
As the demand for diesel fuel and aviation fuel increases worldwide there is increasing interest in sources other than petroleum crude oil for producing the fuels. One such source is what has been termed renewable sources. These renewable sources include, but are not limited to, plant oils such as corn, rapeseed, canola, soybean and algal oils, animal fats such as inedible tallow, fish oils and various waste streams such as yellow and brown greases and sewage sludge. The common feature of these sources is that they are composed of glycerides and Free Fatty Acids (FFA). Both of these compounds contain aliphatic carbon chains having from about 8 to about 24 carbon atoms. The aliphatic carbon chains in the glycerides or FFAs can be saturated or mono-, di- or poly-unsaturated. The glycerides may be tri-glycerides, di-glycerides, mono-glycerides, or any combination thereof.
There are reports in the art disclosing the production of hydrocarbons from oils. For example, U.S. Pat. No. 4,300,009 discloses the use of crystalline aluminosilicate zeolites to convert plant oils such as corn oil to hydrocarbons such as gasoline and chemicals such as para-xylene. U.S. Pat. No. 4,992,605 discloses the production of hydrocarbon products in the diesel boiling range by hydroprocessing vegetable oils such as canola or sunflower oil. Finally, US 2004/0230085 A1 discloses a process for treating a hydrocarbon component of biological origin by hydrodeoxygenation followed by isomerization.
Applicants have developed a process which comprises an optional pretreatment step, and one or more steps to hydrogenate, deoxygenate, hydroisomerize and selective hydrocrack a renewable feedstock, in order to generate both a diesel fuel product and an aviation fuel product.